我手上有几个问题。我的应用程序不断崩溃，当我查看我的 logcat 时，它给了我两个不同的原因。我只需要有人告诉我为什么以及我能做些什么来解决它。
07-27 11:05:53.647: E/AndroidRuntime(913): FATAL EXCEPTION: AsyncTask #2
07-27 10:36:54.139: E/AndroidRuntime(775): java.lang.RuntimeException: An error occured while executing doInBackground()
07-27 10:36:54.139: E/AndroidRuntime(775): at android.os.AsyncTask$3.done(AsyncTask.java:299)
07-27 10:36:54.139: E/AndroidRuntime(775): at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:352)
07-27 10:36:54.139: E/AndroidRuntime(775): at java.util.concurrent.FutureTask.setException(FutureTask.java:219)
07-27 10:36:54.139: E/AndroidRuntime(775): at java.util.concurrent.FutureTask.run(FutureTask.java:239)
07-27 10:36:54.139: E/AndroidRuntime(775): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
07-27 10:36:54.139: E/AndroidRuntime(775): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
07-27 10:36:54.139: E/AndroidRuntime(775): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
07-27 10:36:54.139: E/AndroidRuntime(775): at java.lang.Thread.run(Thread.java:856)
07-27 10:36:54.139: E/AndroidRuntime(775): Caused by: java.lang.NullPointerException
07-27 10:36:54.139: E/AndroidRuntime(775): at com.theproblemsolver.ListView$LoadAllData.doInBackground(ListView.java:92)
07-27 10:36:54.139: E/AndroidRuntime(775): at com.theproblemsolver.ListView$LoadAllData.doInBackground(ListView.java:1)
07-27 10:36:54.139: E/AndroidRuntime(775): at android.os.AsyncTask$2.call(AsyncTask.java:287)
07-27 10:36:54.139: E/AndroidRuntime(775): at java.util.concurrent.FutureTask.run(FutureTask.java:234)
07-27 10:36:54.139: E/AndroidRuntime(775): ... 4 more
我的堆栈跟踪也给了我这些错误......
07-27 11:05:56.119: E/WindowManager(913): Activity com.theproblemsolver.ListView has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView{40d0e800 V.E..... R.....ID 0,0-234,72} that was originally added here
07-27 11:05:56.119: E/WindowManager(913): android.view.WindowLeaked: Activity com.theproblemsolver.ListView has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView{40d0e800 V.E..... R.....ID 0,0-234,72} that was originally added here
07-27 11:05:56.119: E/WindowManager(913): at android.view.ViewRootImpl.<init>(ViewRootImpl.java:354)
07-27 11:05:56.119: E/WindowManager(913): at android.view.WindowManagerGlobal.addView(WindowManagerGlobal.java:216)
07-27 11:05:56.119: E/WindowManager(913): at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:69)
07-27 11:05:56.119: E/WindowManager(913): at android.app.Dialog.show(Dialog.java:281)
07-27 11:05:56.119: E/WindowManager(913): at com.theproblemsolver.ListView$LoadAllData.onPreExecute(ListView.java:85)
07-27 11:05:56.119: E/WindowManager(913): at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:586)
07-27 11:05:56.119: E/WindowManager(913): at android.os.AsyncTask.execute(AsyncTask.java:534)
07-27 11:05:56.119: E/WindowManager(913): at com.theproblemsolver.ListView.onCreate(ListView.java:52)
07-27 11:05:56.119: E/WindowManager(913): at android.app.Activity.performCreate(Activity.java:5104)
07-27 11:05:56.119: E/WindowManager(913): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
27 11:05:56.119: E/WindowManager(913): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
07-27 11:05:56.119: E/WindowManager(913): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
07-27 11:05:56.119: E/WindowManager(913): at android.app.ActivityThread.access$600(ActivityThread.java:141)
07-27 11:05:56.119: E/WindowManager(913): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
07-27 11:05:56.119: E/WindowManager(913): at android.os.Handler.dispatchMessage(Handler.java:99)
07-27 11:05:56.119: E/WindowManager(913): at android.os.Looper.loop(Looper.java:137)
07-27 11:05:56.119: E/WindowManager(913): at android.app.ActivityThread.main(ActivityThread.java:5041)
07-27 11:05:56.119: E/WindowManager(913): at java.lang.reflect.Method.invokeNative(Native Method)
07-27 11:05:56.119: E/WindowManager(913): at java.lang.reflect.Method.invoke(Method.java:511)
07-27 11:05:56.119: E/WindowManager(913): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
07-27 11:05:56.119: E/WindowManager(913): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
07-27 11:05:56.119: E/WindowManager(913): at dalvik.system.NativeStart.main(Native Method)
主要活动
public class MainActivity extends Activity {
EditText et;
Button getanswer;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button getanswer = (Button) findViewById(R.id.button1);
getanswer.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
Intent i = new Intent(MainActivity.this, ListView.class);
startActivity(i);
}
});
}
}
列表视图活动
public class ListView extends ListActivity {
private ProgressDialog pDialog;
JSONParsser jParser = new JSONParsser();
ArrayList<HashMap<String, String>> questionList;
private static String URI = "http://example.com/json";;
//JSONObject json = jParser.getJSONFromURI(URI);
final String TAG_RESULTS = "ResultsSet";
final String TAG_SUBJECT = "Subject";
final String TAG_NUMANSWERS = "NumAnswers";
final String TAG_QUESTION = "Question";
final String TAG_QUESTION_CONTENT = "Content";
final String TAG_QUESTION_CHOSENANSWER = "ChosenAnswer";
final String TAG_QUESTION_ANSWERS = "Answers";
JSONArray ResultsSet = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//setContentView(R.layout.listview);
questionList = new ArrayList<HashMap<String, String>>();
android.widget.ListView lv = getListView();
new LoadAllData().execute();
lv.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,int position, long id) {
}
});
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (resultCode == 100) {
Intent intent = getIntent();
finish();
startActivity(intent);
}
}
class LoadAllData extends AsyncTask<String, String, String> {
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(ListView.this);
pDialog.setMessage("Loading Data. Please wait...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
pDialog.show();
}
protected String doInBackground(String... args) {
try {
JSONObject json = jParser.getJSONFromURI(URI);
ResultsSet = json.getJSONArray(TAG_RESULTS);
for(int i = 0; i < ResultsSet.length(); i++) {
JSONObject r = ResultsSet.getJSONObject(i);
String Subject = r.getString(TAG_SUBJECT);
String NumAnswers = r.getString(TAG_NUMANSWERS);
JSONObject Question = r.getJSONObject(TAG_QUESTION);
String Content = Question.getString(TAG_QUESTION_CONTENT);
String ChosenAnswer = Question.getString(TAG_QUESTION_CHOSENANSWER);
String Answers = Question.getString(TAG_QUESTION_ANSWERS);
HashMap<String, String> map = new HashMap<String, String>();
map.put(TAG_SUBJECT, Subject);
map.put(TAG_NUMANSWERS, NumAnswers);
}
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
protected void onPostExecute(String file_URI) {
pDialog.dismiss();
runOnUiThread(new Runnable() {
public void run() {
ListAdapter adapter = new SimpleAdapter(getBaseContext(), questionList,
R.layout.row,
new String[] { TAG_SUBJECT, TAG_NUMANSWERS }, new int[] {
R.id.Subject, R.id.NumAnswers });
setListAdapter(adapter);
}
});
}
}}
SimpleListItem 活动性
public class SingleListItem extends Activity {
TextView subject;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.setContentView(R.layout.singlelistitem);
subject = (TextView) findViewById(R.id.Subject2);
Intent i = getIntent();
String Subject = i.getStringExtra("TAG_SUBJECT");
subject.setText(Subject);
}
}